The invention pertains to the field of hairdressing and in particular to curling rods for cold permanent waving of hair. Over the years a number of curling rods or permanent wave rods have been developed. The curling rods disclosed in U.S. Pat. Nos. 2,242,850, 2,386,612 and 2,652,840 are directed to the curling of hair as it drys but do not provide means for adequately distributing permanent wave solution to the interior of the curl. U.S. Pat. Nos. 2,825,344 and 2,896,638 disclose rods with interior radial passages to distribute the permanent wave solution. The hard plastic construction of such rods tends to break fine hair especially when the surface is roughened as in U.S. Pat. No. 2,825,344. U.S. Pat. Nos. 2,747,585 and 3,056,413 disclose rods with disposable elements that are broken to release permanent wave solution to the interior of the rod and hair curl. Such rods are not reusable.
Disclosed in U.S. Pat. No. 2,757,676 is a rod of spongy absorbent material to reduce hair breakage and absorb excess permanent wave solution. The spongy material is difficult to clean for reuse and traces of solution from previous use can burn the hair, cause hair breakage and permanently damage the hair until the growth of replacement hair.
The hard plastic grooved rod disclosed in U.S. Pat. No. 2,395,965 or at the other extreme the multiple flexible strands disclosed in U.S. Pat. No. 2,721,560 both tend to produce hair breakage when the tensioned hair curl on the rod is softened by the permanent wave solution. Despite the extensive devlopment of permanent wave rods, difficulties in their use and safety remain.